The present application claims priority from European Patent Application No. 01000523.9, filed Oct. 8, 2001.
The invention relates to a water separator for a gas analyzer, comprising a housing, a first chamber disposed within the housing, a second chamber disposed within the housing, a first wall formed of a gas permeable and liquid impermeable material separating the chambers, means for introducing a gas sample containing a liquid into the first chamber with a first portion of gas passing through the first wall to the second chamber and a second portion of the gas and the liquid remaining in the first chamber, means for flowing said first portion of the gas from the second chamber to a measuring unit, a water receiving means mounted in the housing, and connected to the first chamber for receiving the second portion of the gas and for separating liquid from the second portion of the gas, a third chamber connected to the water receiving means, a fourth chamber, a second wall formed of a gas permeable and liquid is impermeable material separating the third and fourth chambers, the second portion of the gas passing through the second wall to the fourth chamber, and discharge means for discharging the second portion of the gas from the fourth chamber and connecting the water receiving means with a source of vacuum.
For example, when using a CO2 analyzer for measuring alveolar air, a problem encountered is the vapour contained in exhalation air. Since temperature in a sampling passage is lower than the human body temperature, the water vapour condensates in a measuring device and the intrusion of water drops inside a measuring sensor results in the failure of a measurement. In addition, a gas sample often entraps mucus and blood as well as dust which the water separator must also be capable of removing from gas.
In prior known gas analyzers, water has been removed from a gas sample by using a water separator, provided with a water-separation chamber which divides the flow into two partial flows in a manner that the main flow is sucked through a measuring sensor by means of a tube connected with the water-separation chamber and the many times lesser side flow is sucked continuously by way of a tube connected with the bottom section of said water-separation chamber into a water receiver for retaining therein the water contained in a gas sample and further on to a pump.
It has also been known in the art to use a moisture-equalizing tube. In this case, the analyzer is not usually fitted with individual water-separator but, instead, a sampling tube between a patient and the apparatus as well as a tube between a sampling connector in the apparatus and a measuring sensor are made of a material which equalizes moisture of the gas inside the tube to be the same as that on the outside, so that water always tends to find its way towards the drier side, the moisture of a gas sample equalizing to be the same as the moisture of ambient air and no condensation occurs on the tube walls.
This prior art solution involves the following drawbacks. The tube material is only capable of a limited transfer of water through the wall per unit time, whereby the water splashed from the tubing of a respiration apparatus, a patient""s mucus or blood may end up on a measuring sensor. Dust in the air also finds its way to a measuring sensor and causes problems there.
In order to overcome the problems described above a special type water separator has been developed. Said known water separator is described in U.S. Pat. No. 4,886,528.
The device shown in U.S. Pat. No. 4,886,528 operates quite satisfactorily when placed in its normal upright position. When however said device is not in upright position the performance was hindered as soon as some water blocked the filter area leading to the side flow. When the filter area is blocked, the vacuum needed to force mucus and other liquids to a container cannot be obtained.
The object of the present invention is to provide a water separator by means of which the drawbacks of the prior art technique can be eliminated. This has been achieved by means of a water separator of the invention. The invention is characterized in that at least a part of the third chamber is formed to extend over essentially about 360 degrees around a cross sectional area of the housing.
An advantage of the invention is that the device is practically position independent, i.e. the flow by which harmful mucus and other liquids are forced to the container is in any practical positions of the device never totally blocked. Another advantage of the invention is its simplicity whereby the invention can be taken into use and also used with considerably low costs.